As wind blows across the land surface, it picks up small particles of sand. You can demonstrate how wind moves sediment: Cover the bottom of a cake pan with a flat layer of cornmeal (about 2 cm deep). With a straw, gently blow across the surface of the cornmeal. What happens to the surface? Place a small obstruction (small pebble, shell, screw) in the center of the pan and continue to blow. What happens behind the obstruction?